Halogermanides and methods for the preparation thereof

ABSTRACT

A trichlorogermanide of formula (I): [R4N]/[R4P]Cl[GeCl3] (I), where R is Me, Et, iPr, nBu, or Ph, tris(trichlorosilyl)germanide of formula (II): [R4N]/[R4P][Ge(SiCl3)3] (II), where R is Me, Et, iPr, nBu, or Ph, a tris(trichlorosilyl)germanide adduct of GaCl3 of formula (III): [Ph4P][Ge(SiCl3)3*GaCl3], and a tris(trichlorosilyl)germanide adduct of BBr3 of formula (IV): [Ph4P][Ge(SiCl3)3*BBr3]. Also, methods for preparing the trichlorogermanides of formula (I), the tris(trichlorosilyl)germanide of formula (II), the tris(trichlorosilyl)germanide adduct of BBr3 of formula (IV).

CROSS REFERENCE TO RELATED APPLICATIONS

The present application application is a divisional of U.S. Pat.Application 17/308,590 filed May 5, 2021, pending, which is a divisionalof U.S. Pat. Application 16/774,682, filed on Jan. 28, 2020, now U.S.Pat. No. 11,053,263, which is a continuation of U.S. Pat. Application15/994,304, now U.S. Pat., 10,618,921, filed on May 31, 2018, whichclaims priority to EP Application No. 17173959.2, filed on Jun. 1, 2017,the entire contents of each of which are hereby incorporated byreference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to novel halogermanides and a method forthe preparation thereof.

Description of the Related Art

Halosilanes, polyhalosilanes, halogermanes, polyhalogermanes, silane,polysilanes, germane, polygermanes and corresponding mixed compoundshave long been known, cf., in addition to the customary text books ofinorganic chemistry, also WO 2004/036631 A2 or C.J. Ritter et al., J.Am. Chem. Soc., 2005, 127, 9855-9864.

L. Müller et al. in J. Organomet. Chem., 1999, 579, 156-163 describe,inter alia, the preparation of trichlorosilylmethylgermanes.

Methylgermylsilanes and phenylgermylsilanes are known from Angew. Chem.,1993, 105, 587-588 (G. Sih et al.) and also from Tetrahedron Lett.,1970, 51, 4443-4447 (F. Feher et al.).

Furthermore, phenyl- and hydrogen-containing compounds are known inwhich Sn—Si and Sn—Ge bonds are present (J.B. Tice et al., J. InorganicChemistry, 2009, 48(13), 6314-6320). Here, it is suggested to use thesecompounds as IR semiconductors.

In patent document US 7,540,920 B2, Singh et al. disclose Si—Gecompounds of the formula X₁X₂X₃ —Si—Ge— X₄X₅X₆ having hydrogen orhalogen radicals X₁₋₆.

BRIEF SUMMARY OF THE INVENTION

Practically nothing is currently known about chlorosilylarylgermanes.Thus, by means of basic research, effort is being made to find novelcompounds and to seek novel preparation routes, in particular also withrespect to potential industrial and optionally improvable applications.

The object of the present invention is to provide novel germanium andsilicon-germanium compounds and also a method for the preparationthereof.

New synthetic possibilities for preparing silicon-germanium compounds,particularly

-   R₃Ge—SiCl₃,-   Cl₃Si—GeR₂—GeR₂—SiCl₃,-   Cl₃Ge—SiCl₃,-   [Ph₄P][Ge(SiCl₃)₃],-   [Ph₄P][Ge(SiCl₃)₃*GaCl₃],-   [Ph₄P][Ge(SiCl₃)₃*BBr₃]

by the reaction of chlorinated or perchlorinated, organic or inorganicgermanium compounds of the type R_(n)GeCl_(4-n) (n = 0,2,3) withhexachlorodisilane with addition of catalytic amounts of an ammoniumchloride salt [R₄N]Cl where the radicals R = Me, Et, iPr, nBu werepresented in the patent applications entitled “NeueChlorsilylarylgermane, Verfahren zu deren Herstellung und derenVerwendung” (Novel chlorosilylarylgermanes, methods for preparationthereof and use thereof) and “Triphenylgermylsilan, Verfahren zurHerstellung und seine Verwendung” (Triphenylgermylsilane, method ofpreparation and its use). By means of the reaction, varioussilicon-germanium compounds are obtained.

In addition, it has been found that reactants of the type R₃GeCl areconverted by the reaction with Si₂Cl₆ in the presence of ammoniumchloride, whereupon a Ge—Si bond is formed at the Ge—Cl position. In thereaction of R₂GeCl₂ with Si₂Cl₆/ammonium chloride, the Ge—Si bondformation takes place at only one Ge—Cl position. In addition, Ge—Gebond formation occurs at the second Ge—Cl position. Thegermanium-silicon compound thus found or prepared can be converted withLiAlH₄ to silicon hydride compounds. In the context of the invention,such compounds are prepared by the synthesis of Ph₃Ge—SiH₃ fromPh₃Ge—SiCl₃ for example. In the case of reactions of compounds of thetype R_(n)GeCl_(4-n) (n = 0), different reactions take place dependingon the stoichiometry.

-   [R4N][GeCl3] salts (GeCl4:Si2Cl6:[R4N]Cl, 1:1:1),-   Cl₃Si—GeCl₃(GeCl4:Si2Cl6:[R4N]Cl, 1:1:0.1), or-   [Ph4P][Ge(SiCl3)3] (GeCl4:Si2Cl6:[Ph4P]Cl, 1:4:1)

were produced. [Ph₄P][Ge(SiCl₃)₃] can be reacted with Lewis acids,abbreviated to “LA”, to give the corresponding adducts[Ph₄P][Ge(SiCl₃)₃*LA]. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THEDRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1A: Crystal Structure of trichlorosilyltriphenylgermane (1).

FIG. 1B: ²⁹Si-NMR spectrum of the crude product of the synthesis oftrichlorosilyltriphenylgermane (1).

FIG. 2 : Crystal Structure of1,2-bis(trichlorosilyl)-1,1,2,2-tetraphenyldigermane (2).

FIG. 3 : ²⁹Si-NMR spectrum of trichlorosilyltrichlorogermane (3).

FIG. 4 : Crystal structure of trichlorogermanide (4).

FIG. 5A: Crystal structure of tris(trichlorosilyl)germanide (5).

FIG. 5B: ²⁹Si-NMR spectrum of tris(trichlorosilyl)germanide (5).

FIG. 6A: Crystal structure of tris(trichlorosilyl)germanide adduct ofGaCl₃ (6).

FIG. 6B: ²⁹Si-NMR spectrum of tris(trichlorosilyl)germanide adduct ofGaCl₃ (6).

FIG. 7A: Crystal structure of tris(trichlorosilyl)germanide adduct ofBBr₃ (7).

FIG. 7B: ²⁹Si-NMR spectrum of tris(trichlorosilyl)germanide adduct ofBBr₃ (7).

DETAILED DESCRIPTION OF THE INVENTION

In the context of the invention, the measure “equivalent”, “eq.” forshort, is understood to mean the amount of catalyst in mol based on theamount of hexachlorodisilane in mol. For example, 0.1 eq of catalystdenotes 0.1 mol of catalyst per mole of hexachlorodisilane or 10 mol% ofcatalyst based on hexachlorodisilane.

In the context of the invention, “hexachlorodisilane” is alsoabbreviated to “HCDS”.

Chlorosilylarylgermanes are prepared by

-   (a) dissolving an arylchlorogermane with hexachlorodisilane in a    solvent and-   (b) reacting in the presence of a catalyst at a temperature of 5 to    40° C., wherein the aryl groups of the arylchlorogermane are each    independently phenyl.

The chlorosilylarylgermanes can be selected from the series comprisingtrichlorosilyltriphenylgermane and/or1,2-bis(trichlorosilyl)-1,1,2,2-tetraphenyldigermane.

Step (b) of said preparation method can be carried out at roomtemperature.

In step (a) of the method, a triarylchlorogermane may be used in a molarratio to hexachlorodisilane of 1:1 and/or a diaryldichlorogermane may beused in a molar ratio to hexachlorodisilane of 1:2.

Furthermore, it is possible to use an arylchlorogermane from the seriescomprising triphenylchlorogermane and/or diphenyldichlorogermane.

The solvent used in step (a) may be selected to be inert in order toavoid undesired reactions with HCDS. Furthermore, dichloromethane may beused since this does not react with HCDS in the chosen temperatureranges.

When carrying out the method according to the invention, phosphoniumchlorides [R₄P]Cl or ammonium chloride salts [R₄N]Cl may be used ascatalyst, where the radicals R are selected from Me, Et, iPr, nBu, Ph.

In this case, the reaction proceeds more slowly the less catalyst used.On the other hand, excessively large amounts of catalyst are undesirablesince this has to be removed at the end of the reaction. The method canbe carried out economically with respect to the separation complexity ifthe catalyst is used in an amount of 0.001 to 1 mol per mole ofhexachlorodisilane. The method is carried out particularly favourably if0.01 to 0.1 mol is used per mole of hexachlorodisilane.

A further aspect of carrying out the method economically is theselection of the amount of solvent. In the method, at least 5 mol ofsolvent can be used per mole of hexachlorodisilane, preferably 10 mol to100 mol of solvent per mole of hexachlorodisilane.

In the method, the reaction may be carried out with thorough mixing,preferably with stirring, and over a period of 1 to 24 hours, preferablyover the course of 12 h, and further preferably under protective gas,preferably under nitrogen or argon. The solvent can be subsequentlyremoved. This can be undertaken preferably in a dry oxygen-freeenvironment, particularly preferably in an isolated environment, forexample in a glove box, and further preferably at standard pressure orunder reduced pressure, preferably in the range of 1 to 500 hPa, whereinchlorosilylarylgermanes are obtained as crystalline product.

The trichlorosilyltrichlorogermane molecule of interest can also beprepared, which has already been disclosed by Singh et al. (US 7,540,920B2) without a method of preparation. For this purpose, GeCl₄ is usedinstead of the arylchlorogermane. The conversion reaction withhexachlorodisilane is then subsequently carried out in a solvent and inthe presence of a catalyst.

In the preparation of trichlorosilyltrichlorogermane, GeCl₄ is dissolvedwith hexachlorodisilane in a solvent and the reaction is conducted inthe presence of a catalyst at a temperature of 5 to 40° C.

It can be advantageous to use the catalyst in amounts of 0.001 to 1 eq.,preferably 0.01 to 0.1 eq. Example 3 describes an exemplary procedure ofthis method.

If this method is further modified by using the ammonium chloride salt[R₄N]Cl or phosphonium chloride salts [R₄P]Cl in a stoichiometric amountinstead of a catalytic amount, preferably from 0.5 to 1.5 eq.,particularly preferably 1 eq., then halogermanides are surprisinglyobtained, namely trichlorogermanide on using [R₄N]Cl.

The invention therefore provides trichlorogermanides of the generalformula I

where R = Me, Et, iPr, nBu.

In the context of the invention, “[R₄N]/[R₄P]Cl” in the formula I isunderstood to mean that phosphonium or ammonium salts are obtained.

The invention also relates to a method for preparing trichlorogermanides(I) according to the invention, by dissolving GeCl₄ withhexachlorodisilane in a solvent and reacting in the presence of astoichiometric amount of [R₄N]Cl or [R₄P]Cl at a temperature of 5 to 40°C.

Example 4 describes a preferred procedure where R = nBu.

The synthesis carried out according to Example 4 presents a novelpossibility of obtaining [R₄N][GeCl₃] salts and [R₄P]Cl[GeCl₃] salts, byvarying the cation [R₄N]⁺ or [R₄P]⁺ and by using the desired chloridesalt for the heterolytic cleavage of Si₂Cl₆. This is particularlyinteresting since it has been found that the cation determines how wella compound crystallizes.

For instance, a large variety of [R₄N][GeCl₃] salts and [R₄P]Cl[GeCl₃]salts can be prepared in accordance with the invention.

If, in a modification of the method, the starting materials Si₂Cl₆ andGeCl₄ are used in a ratio of 4:1 with addition of stoichiometric amountsof [R₄N]Cl or [R₄P]Cl, tris(trichlorosilyl)germanide is surprisinglyobtained.

For example, [Ph₄P]Cl can be used (Example 5).

The invention likewise provides tris(trichlorosilyl)germanide of theformula II,

The invention therefore likewise provides a method for preparing thetris(trichlorosilyl)germanide (II) according to the invention, bydissolving hexachlorodisilane with GeCl₄ in a solvent and reacting inthe presence of a stoichiometric amount of [R₄N]Cl or [R₄P]Cl at atemperature of 5 to 40° C.

A preferred ratio of hexachlorodisilane to GeCl₄ is 4:1.

The stoichiometric amount used is preferably from 0.5 to 1.5 eq.,particularly preferably 1 eq.of [R₄N]Cl or [R₄P]Cl. An illustrativesynthesis of the germanide (II) according to the invention is moreparticularly elucidated in Example 5.

If the tris(trichlorosilyl)germanide according to the invention orobtained according to the invention is reacted with GaCl₃,tris(trichlorosilyl)germanide adduct of GaCl₃ is obtained:

The invention therefore likewise provides the adduct of the formula III,

and likewise the method for preparation thereof by mixing thetris(trichlorosilyl)germanide according to the invention or obtainedaccording to the invention with GaCl₃ and dissolving the resultingmixture in dichloromethane with stirring, whereupon the adduct III isobtained at a temperature of 5 to 40° C. over a period of 1 to 24 hours.

A more detailed elucidation of the synthesis is specified in Example 6.

Instead of the reaction according to the invention oftris(trichlorosilyl)germanide with GaCl₃, tris(trichlorosilyl)germanidecan be reacted with BBr₃. In this case, thetris(trichlorosilyl)germanide adduct of BBr₃ is found.

The invention therefore likewise provides the adduct of the formula IV,

and likewise the method for preparation thereof by mixing thetris(trichlorosilyl)germanide according to the invention or obtainedaccording to the invention with BBr₃ and dissolving the resultingmixture in dichloromethane with stirring, whereupon the adduct IV isobtained at a temperature of 5 to 40° C. over a period of 1 to 120hours.

A more detailed elucidation of this synthesis is specified in Example 7.

The Ge or Si-Ge compounds according to the invention or prepared inaccordance with the invention may serve as precursors for materialswhich are used for the controlled deposition of thin Si-Ge layers.

The examples which follow provide additional illustration of the presentinvention without restricting the subject matter. The term “roomtemperature” is abbreviated to “RT” in the examples.

Analytical Methods for Determination of the Crystal Structure

The data for all structures were collected at 173 K using a STOE IPDS IIdual beam diffractometer using a Genix microfocus tube with mirroroptics using MoK_(α)radiation (λ = 0.71073 Å) and scaled using the framescaling procedure of the X-AREA program (Stoe & Cie, 2002). Thestructures were solved by direct methods with the aid of the SHELXSprogram (Sheldrick, 2008) and refined on F² by the full matrix leastsquares technique. Cell parameters were determined by refinement on θvalues of the reflections with I>6σ(I).

Input Materials

Hexachlorodisilane, “HCDS” for short, GeCl₄ from Evonik Industries AG,triphenylchlorogermane, diphenyldichlorogermane.

Example 1: Preparation of Trichlorosilyltriphenylgermane (1)

The synthesis was carried out according to Equation 1 from Ph₃GeCl andSi₂Cl₆ with addition of a catalytic amount of 0.1 eq of [nBu₄N]Cl.

Equation 1: Reaction of Ph₃GeCl and Si₂Cl₆ with addition of a catalyticamount of 0.1 eq of [nBu₄N]Cl.

To a clear colourless solution of 500 mg, corresponding to 1.47 mmol, ofPh₃GeCl and 40 mg or 0.14 mmol of [nBu₄N]Cl in 5 ml or 78.3 mmol ofCH₂Cl₂ were added at room temperature while stirring 400 mg,corresponding to 1.49 mmol, of Si₂Cl₆. A clear colourless reactionsolution was obtained which was stirred at room temperature over thecourse of 12 h. A crude product in the form of a colourless crystallinesolid 1 could be isolated from the reaction solution after slow removalof the solvent. The yield was 59%. The crude product still comprised upto about 30% of the reactant Ph₃GeCl. By X-ray diffractometry, it waspossible to determine the crystal structure of 1 (FIG. 1A). The unmarkedatoms in the figure represent hydrogen.

The ²⁹Si-NMR spectrum of 1 is shown in FIG. 1B.

All results of a ¹H, ¹³C and ²⁹Si NMR spectroscopic investigation:

-   ²⁹Si-NMR (99.4 MHz, CD₂Cl₂, 298 K):-   δ = 13.3.-   ¹H-NMR (500.2 MHz, CD₂Cl₂, 298 K):-   δ = 7.58 (m); 7.75 (dd ³J(H,H) = 8.0 Hz, ²J(H,H) = 1.4 Hz).-   ¹³C-NMR (125.0 MHz, CD₂Cl₂, 298 K):-   δ = 128.9; 130.1; 132.2; 135.3.

Example 2: Preparation of1,2-Bis(Trichlorosilyl)-1,1,2,2-Tetraphenyldigermane (2)

The synthesis was carried out according to Equation 2 from Ph₂GeCl₂ andSi₂Cl₆ with addition of catalytic amounts (0.1 eq) of [nBu₄N]Cl.

Equation 2: Reaction of Ph₂GeCl₂ and Si₂Cl₆ with addition of catalyticamounts (0.1 eq) of [nBu₄N]Cl.

To a clear colourless solution comprising 500 mg or 1.68 mmol ofPh₂GeCl₂ and 90 mg or 0.32 mmol of [nBu₄N]Cl in 5 ml or 78.3 mmol ofCH₂Cl₂, Si₂Cl₆ was added at room temperature. The resulting reactionsolution was subsequently stirred over the course of 12 h.

A crude product 2 could be obtained in a yield of 77% from the reactionsolution after slow removal of the solvent which could be isolated byextraction with Et₂O and subsequent crystallization. The yield in thiscase was 57%. By X-ray diffractometry, it was possible to determine thecrystal structure of 2, shown in FIG. 2 .

All results of a ¹H, ¹³C and ²⁹Si NMR spectroscopic investigation:

-   ²⁹Si-NMR (99.4 MHz, CD₂Cl₂, 298 K):-   δ = 12.3-   ¹H-NMR (500.2 MHz, CH₂Cl_(2,) 298 K):-   δ = 7.41 (t ³J(H,H) = 7.2 Hz (2H)), 7.47 (d ³J(H,H) = 7.2 Hz (1H)),    7.56 (d ³J(H,H) = 7.2 Hz (2H)).-   ¹³C-NMR (125.0 MHz, CH₂Cl_(2,) 298 K):-   δ= 129.0; 130.1; 131.8; 136.0.

Example 3: Preparation of Trichlorosilyltrichlorogermane (3)

The synthesis was effected according to Equation 3 from GeCl₄ and Si₂Cl₆(1:1) with addition of 0.1 eq. of [nBu₄N]Cl as a catalytic amount.

Equation 3: Reaction of GeCl₄ and Si₂Cl₆ (1:1) with addition of acatalytic amount (0.1 eq.) of the catalyst where R = Bu: [nBu₄N]Cl.

To a clear colourless solution comprising 100 mg or 0.4 mmol of[nBu₄N]Cl in a 30:70 mixture of GeCl₄ and CH₂Cl₂ was added at roomtemperature 1 g or 3.7 mmol of Si₂Cl₆ and the reaction mixture thusobtained was stirred at room temperature over the course of 12 h. Theproduct 3 was condensed with other volatile constituents from thereaction solution into a nitrogen-cooled receiver. Subsequentdistillation at 140° C. at 1013 hPa resulted in the isolation of pure 3as a clear colourless liquid in a yield of 22%.

The ²⁹Si-NMR spectrum of 3 is shown in FIG. 3 .

All results of a ²⁹Si-NMR spectroscopic investigation:

-   ²⁹Si-NMR (99.4 MHz, CH₂Cl_(2,) 298 K):-   δ = - 6.3.

Example 4: Preparation of trichlorogermanide (4).

The procedure was as in Example 3 but with the difference that [nBu₄N]Clwas used in a stoichiometric amount synonymous to 1 eq.The conversionreaction was effected in a redox reaction according to Equation 4.

Equation 4: Reaction of GeCl₄ and Si₂Cl₆ (1:1) with addition of astoichiometric amount, namely 1 eq., of [nR₄N]Cl where R = Bu.

To a clear colourless solution of 300 mg or 1.4 mmol of GeCl₄ and 390 mgor 1.4 mmol of [nBu₄N]Cl in CH₂Cl₂ were added at room temperature 375 mgor 1.4 mmol of Si₂Cl₆ and the reaction mixture thus obtained was stirredover the course of 12 h. Trichlorogermanide 4 could be isolated from thereaction solution as a yellow crystalline solid after slow removal ofthe solvent. By means of X-ray diffractometry, the structure of 4 couldbe determined, shown in FIG. 4 . For reasons of clarity, the cation[nBu₄N]⁺ is not depicted here.

Example 5: Preparation of Tris(Trichlorosilyl)Germanide (5)

The synthesis was effected according to Equation 5 from GeCl₄ and Si₂Cl₆in a molar ratio of 1:4 with addition of a stoichiometric amount, inthis case 1 eq., of [Ph₄P]Cl.

Equation 5: Reaction of GeCl₄ and Si₂Cl₆ (1:4) with addition of astoichiometric amount (1 eq.) of [Ph₄P]Cl.

To a clear colourless solution comprising 93 mg or 0.4 mmol of GeCl₄ and163 mg or 0.4 mmol of [Ph₄P]Cl in CH₂Cl₂ as solvent were added at roomtemperature 478 mg or 1.7 mmol of Si₂Cl₆ and the reaction mixture thusobtained was stirred over the course of 12 h. 5 could be isolated in 99%yield from this mixture as a yellow crystalline solid after slow removalof the solvent. By means of X-ray diffractometry, the crystal structureof 5 could be determined, shown in FIG. 5A. For reasons of clarity, thecation [Ph₄P]⁺ is not depicted here.

In this reaction there is a reduction of the GeCl₄. In addition, athree-fold silylation of the germanium atom takes place.

The ²⁹Si-NMR spectrum of 5 is shown in FIG. 5B.

All results of a ¹H- and ²⁹Si-NMR spectroscopic investigation:

-   ²⁹Si-NMR (99.4 MHz; CD₂Cl₂; 298 K):-   δ = 29.7.-   ¹H-NMR (500.2 MHz; CD₂Cl₂; 298 K):-   δ = 7.54 (qd ³J(H,H) = 4.5 Hz; ²J(H,H) = 1.3 Hz; (2H)); 7.68 (td    ³J(H,H) =7.4 Hz; ³J(H,H) = 3.4 Hz (2H)); 7.84 (tt ³J(H,H) = 7 Hz;    ²J(H,H) = 1.0 Hz (1H)).

Example 6: Preparation of Tris(Trichlorosilyl)Germanide Adduct of GaCl₃(6)

The synthesis of 6 was effected according to Equation 6 fromtris(trichlorosilyl)germanide (5) and GaCl₃.

Equation 6: Reaction of 5 with GaCl₃.

50 mg or 0.1 mmol of 5 and 10 mg or 0.1 mmol of GaCl₃ were mixed assolids at room temperature and subsequently dissolved completely inCH₂Cl₂. The clear yellow reaction mixture was stirred at roomtemperature over the course of 12 h. 6 could be obtained from the clearyellow reaction solution as a yellow crystalline solid in a yield of 82%after slow removal of the solvent.

By means of X-ray diffractometry, the crystal structure of 6 could bedetermined, shown in FIG. 6A. For reasons of clarity, the cation [Ph₄P]⁺is not depicted here.

The ²⁹Si-NMR spectrum of 6 is shown in FIG. 6B.

All results of a ¹H- and ²⁹Si-NMR spectroscopic investigation:

-   ²⁹Si-NMR (99.4 MHz, CD₂Cl₂, 298 K):-   δ = 11.3.-   ¹H-NMR (500.2 MHz; CD₂Cl₂; 298 K):-   δ = 7.54 (qd ³J(H,H) = 4.5 Hz; ²J(H,H) = 1.3 Hz; (2H)); 7.68 (td    ³J(H,H) =7.4 Hz; ³J(H,H) = 3.4 Hz (2H)); 7.84 (tt ³J(H,H) = 7 Hz;    ²J(H,H) = 1.0 Hz (1H)).

Example 7: Preparation of Tris(Trichlorosilyl)Germanide Adduct of BBr₃(7)

The synthesis of 7 was effected according to Equation 7 fromtris(trichlorosilyl)germanide (5) and BBr₃.

Equation 7: Reaction of 5 with BBr₃.

BBr₃ was added at room temperature to a clear yellow solution of 5 inCH₂Cl₂. After 4 days, colourless crystals had precipitated from theyellow reaction solution thus obtained. By means of X-raydiffractometry, the crystal structure of 7 could be determined, shown inFIG. 7A. For reasons of clarity, the cation [Ph₄P]⁺ is not depictedhere.

The ²⁹Si-NMR spectrum of 7 is shown in FIG. 7B.

All results of a ¹¹B- and ²⁹Si-NMR spectroscopic investigation

-   ²⁹Si-NMR (99.4 MHz, CD₂Cl₂, 298 K):-   δ = 12.3.-   ¹¹B-NMR (160.5 MHz; CD₂Cl₂; 298 K):-   δ = -17.5.

The invention claimed is:
 1. A method for preparing atris(trichlorosilyl)germanide adduct of BBr₃ of formula (IV):

the method comprising: mixing tris(trichlorosilyl)germanide of formula(II):

wherein R = Ph, with BBr₃, to obtain a mixture; dissolving the resultingmixture in dichloromethane with stirring; and obtaining thetris(trichlorosilyl)germanide adduct at a temperature of 5 to 40° C.over a period of 1 to 120 hours.